Core support is requested for a Staff Assistant, a Laboratory Assistant, and a Research Technician responsible for respectively; 1) budgetary, administrative, and clerical activities; 20 maintenance of medium solutions, instrument and glassware preparation; and 3) maintenance of a barrier-sustained isolator nuclear colony of athymic mice and rats and a breeding colony of athymic mice and rats derived from that nuclear colony. This Research Technician also is responsible for passage of human brain tumor xenografts and growth and supply of those xenografts to individual projects which then grow them for studies as they are needed.